Field of the Invention
The present invention relates to a touch display device which is capable of improving resolution and visibility.
Discussion of the Related Art
A touch panel is an input device that allows a user to input a command by selecting an instruction, displayed on the screen of a display device or the like, with the hand or an object. That is, the touch panel converts a contact position, which is contacted by the user's hand or an object, into an electrical signal, and receives an instruction, selected at the contact position, as an input signal. The touch panel may replace a separate input device that is operated in the state of being connected to a display device, such as a keyboard or a mouse, and thus the range of use thereof is gradually increasing.
The touch panel described above is attached to the front surface of a liquid crystal display. At this time, in the liquid crystal display, because display electrodes are regularly arranged in respective pixel areas, and thus serve as a diffraction grid, a plurality of diffracted images may be generated by the display electrodes depending on the wavelength of the light that is emitted from a backlight unit and passes through the display electrodes, which may cause constructive interference.
In addition, in the touch panel, because touch-sensing electrodes are also regularly arranged and serve as a diffraction grid, a plurality of diffracted images may be generated by the touch-sensing electrodes depending on the wavelength of the light that is directed from the display panel and passes through the touch-sensing electrodes, which may cause constructive interference.
At this time, because the touch-sensing electrodes and the display electrodes are designed without giving consideration to the arrangement relationship therebetween, the images diffracted by the touch-sensing electrodes differ from the images diffracted by the display electrodes. Therefore, as illustrated in FIG. 1, matrix scattering caused by the images diffracted by the display electrodes and matrix scattering caused by the images diffracted by the touch-sensing electrodes are strongly generated in different directions. Accordingly, visual deteriorations attributable to the reflection of ambient light (e.g. double images and color-shift) may occur, which causes deterioration in image visibility.